1. Field of the Invention
This invention is generally concerned with apparatus and methods for producing liquid (e.g., aqueous or non-aqueous liquid systems) chlorine dioxide (ClO2). This compound is normally produced by either oxidation of chlorite compounds such as sodium chlorite (NaClO2) or by reduction of chlorate compounds such as sodium chlorate (NaClO3).
By way of a first example of these technologies, U.S. Patent Application Publication No. US2005/0244328 A1 (“the '328 Publication”) teaches use of a chemical reactor that receives three distinct precursor chemicals and chemically reacts them to produce chlorine dioxide gas. These three precursor chemicals are sodium hypochlorite (NaOCl, a halogen donor), sodium chlorite (NaClO2, a chloride donor) and sodium bisulfate (NaHSO4). One likely reaction sequence of these three chemicals is as follows:NaOCl+NaHSO4→HOCl+Na2SO4  (I)HOCl+H→½Cl2+H2O  (II)NaClO2+½Cl2→NaCl+ClO2  (III)
That is to say that, per reaction (I), the sodium hypochlorite reacts with sodium bisulfate to produce hypochlorus acid. Per reaction (II), the hypochlorus acid produced by reaction (I) reacts with excess free hydrogen ions to produce chlorine gas in solution (such excess free hydrogen ions result from acidic reaction conditions maintained in the reaction system). Then, in reaction (III), the chlorine gas reacts with the sodium chlorite to produce chlorine dioxide gas.
The '328 Publication also teaches that, for reasons of safety, its reaction chamber must be operated under elevated pressures and within a specified temperature range. Be that as it may, the gaseous chlorine dioxide product formed in the reaction chamber taught by the '328 Publication is then forced through an extended exit pipe (see item number 26 of FIG. 2 of the '328 Publication) and then out of a discharge orifice located at the end of the extended exit pipe 26. Thereafter, the chlorine dioxide gas is injected into a stream of waste water in order to purify it.
U.S. Pat. No. 6,645,457 B2 (“the '457 patent”) teaches a vacuum-driven chlorine dioxide generator having a tuned reaction zone in the form of a hollow frustum wherein various precursor ingredients are chemically reacted to form chlorine dioxide gas. The preferred reactants for the practice of this invention are an aqueous solution of sodium chlorite (NaClO2) and chlorine gas (Cl2). In an alternative embodiment, aqueous hydrochloric acid (HCl) and sodium hypochlorite (NaOCl) can be reacted to produce chlorine gas which in turn is reacted with sodium chlorite (NaClO2) to produce chlorine dioxide (ClO2) gas. Using either of these methods, the chlorine dioxide gas is produced according to the idealized reaction:NaClO2+Cl2→2ClO2(g)+NaCl
This gaseous ClO2 is then drawn into a stream of water by means of a vacuum created by water being forced through a jet eductor. Upon being drawn into that water the ClO2 gas is converted into an aqueous chlorine dioxide (ClO2) solution.
It should also be noted here that the ClO2 created in the above-noted frustrum-configured reaction zone must travel, in a gaseous state, through a relatively long column 52 (long—relative to the architecture employed in Applicants' invention as hereinafter more fully explained) before it is educted into the water stream being forced through the jet eductor. That is to say that the ClO2 gas created in the reaction zone continues to exist in a gaseous state while it travels over the relatively long column 52 that connects the reaction zone with the jet eductor.
2. Background of Invention
These prior art technologies have certain inherent problems. Not the least of these is the fact that, under many commonly encountered operating temperatures and pressures, chlorine dioxide exists as a gas—and that gas can be highly dangerous. Indeed, owing to its proclivity toward (explosive) decomposition, chlorine dioxide gas and/or solutions containing chlorine dioxide (from which the ClO2 could be released during transport) cannot be safely shipped. Hence, ClO2 is generated at the point of use.
Those skilled in this art will appreciate that ClO2 gas educting devices such as the jet eductor taught in the '457 patent are prone to clogging. Hence high quality water must often be, at considerable expense, brought to remote field locations were such jet eductors are employed. It should also be appreciated that such jet eductor devices do not lend themselves to precise control relative to pump driven fluid injection-driven devices. Moreover, jet eductors are inherently incapable of operating over those wide fluid throughput ranges that are commonly required at many jobsites.